There’s a big difference in how plugins are treated in MySQL and how they are treated in Drizzle. The MySQL way has been to create a C API in front of the C++-like (I call it C- as it manages to take the worst of both worlds) internal “API”. The Drizzle way is to have plugins be first class citizens and use exactly the same API as if they were inside the server.
This means that MySQL attempts to maintain API stability. This isn’t something worth trying for. Any plugin that isn’t trivial quickly surpasses what is exposed via the C API and has to work around it, or, it’s a storage engine and instead you have this horrible mash of C and C++. The byproduct of this is that no core server features are being re-implemented as plugins. This means the API is being developed in a vacuum devoid of usefulness. At least, this was the case… The authentication plugin API seems to be an exception, and it’s interesting to note that semisync replication is in fact a plugin.
So times may be changing… sort of. Yesterday I noted that some storage engine API features are only available if you’re InnoDB and I’ve voiced my general disappointment in the audit API being unsuitable to implement various forms of query logging already in the server (general query log, slow query log).
One thing to note: when the API is the same for both inside the server and a plugin, it makes initial refactoring very easy, and you quickly see the bits that could be improved.